Apparatus and method for heating frying oil with solid-state RF energy technology

ABSTRACT

The present invention relates to a processing apparatus, in which a flying oil is heated, disinfected and/or pasteurized, sterilized. The present invention further relates to a method to treat a flying oil with radio-frequency wave

The present invention relates to a processing apparatus, in which a product is transported from an entry to an exit and is fried in a frying oil. The present invention further relates to a method heat a frying oil with radio-frequency waves.

In a conventional industrial continuous fryer, used to fry for instance meat products, the frying oil is heated up till approximately 180° C. depending on the products to be fried. Products to be fried enter the fryer via a conveyor and the products will be guided through the fryer via one or more conveyors, preferably a lower conveyor in combination with a hold down conveyor. Via the lower conveyor the products will exit the fryer. A heat exchanger is applied within the fryer, preferably at the bottom of the fryer. In a known embodiment, electrical elements positioned in stainless steel tubes will heat up the frying oil which flows around the tubes. In another known embodiment thermal oil flows through stainless steel tubes of the heat exchanger. In the latter case the entrance temperature of the thermal oil in the fryer is approximately 250° C. and the exit temperature out of the fryer is approximately 200° C. However, in the apparatus according to the state in the art, it is impossible to control the temperature of the frying oil accurately, so that in most cases, the frying oil is too hot and hence degrades relatively fast, which leads to increased production cost and a relatively energy inefficient mode of operation.

It is therefore the objective of the present invention to provide a processing apparatus and a method that do not comprise the deficiencies according to the state in the art.

The problem is attained with a processing apparatus, in which a product is transported from a product-entry to a product exit and is fried in a frying oil, wherein the frying oil is pumped by a pump through a microwave chamber and is thereby heated and wherein the microwave chamber comprises at least one, preferably a multitude, solid-state radio frequency source(s).

The disclosure made regarding this subject matter of the present invention also applies to the other invention and vice versa. Subject matters disclosed regarding this invention can also be combined with subject matters from other inventions of the present application.

The present invention relates to a fryer, in which a product is fried. Such a product can be meat-, a cheese, a vegetable product or a combination thereof. The frying takes place in an oil bath, that has preferably a temperature around 180° C. The product is transported through the oil bath from a product-entry to a product-exit, for example by conveyor means or in a moving cage. The product is preferably submerged into the oil bath. The product-entry and the product-exit can be one and the same. However, preferably, the product-entry and the product-exit are spaced apart. The frying process can be batch, continuous or semi-continuous.

The products to be fried preferably enter the inventive processing apparatus via a conveyor and more preferably, the products will be guided through the apparatus via one or more conveyors, even more preferably a lower conveyor in combination with a hold down conveyor. Via the lower conveyor the products preferably exit the fryer.

According to the present invention, the frying oil is pumped by a pump or the like through a microwave chamber and is thereby heated, The microwave chamber comprises at least one, preferably a multitude, solid-state radio frequency source(s), each with a solid-state radio frequency (RF)-transistor(s) in a RF power amplifier. A radio frequency power amplifier is an electronic amplifier, that converts a low power radio frequency signal into a higher power signal. Typically, RF-power amplifiers drive the antenna of a transmitter. The antenna can be coupled to and/or located in a waveguide, wherein the antenna can radiate the microwaves into the waveguide which preferably is designed of reflective material and can guide the microwaves to a desired location, for example into the frying oil chamber wherein the products to be treated are located. Compared to a magnetron, an advantages of a solid-state RF energy technology is a low voltage drive, semiconductor reliability and lower energy consumption due to the advanced control system.

The microwave chamber with the solid-state radio frequency source(s) is used to heat, heat up a frying oil. A frying oil according to the present invention, is any oil used in the industry to a fry a consumable product.

The inventive processing apparatus further comprises a pump which transports, pumps the frying oil past the solid-state radio frequency source(s). The pump can be any means known by the person skilled in the art to move a liquid. The pump can also be means, which add a certain potential energy to the frying oil, so that it can driven by gravitational force past the solid-state radio frequency source(s). The capacity, i.e. the pressure differential and/or the volume-flow of the pump is preferably controllable. Preferably, the pump is controlled based on the temperature of the frying oil in the bath and/or based on the energy provided by the solid-state radio frequency source(s). The pump and hence the flow of the frying oil through the fryer can also be utilized to influence the heat transfer between the frying oil and the product to be fried. Turbulent or laminar heat transfer conditions or a mixture thereof can be achieved in the inventive processing apparatus.

For heating purposes, the frying oil flows out of the bath towards the microwave chamber, where it is heated and then flows back into the bath of the fryer. There can be numerous locations in the fryer, where the frying oil is removed and/or numerous locations where the frying oil is fed back into the fryer. One or more entries and/or one or more exits may each be equipped with a valve in order to adjust the flow towards or from the fryer. Within the fryer the frying oil is preferably flowing in the same direction as the direction of the product flow. This may be advantageous in order to prevent distortion of the position of the food products on the conveyor and to achieve that sediment such as loosen particles, for instance coating in case of coated products, can be collected and discharged via a preferably build-into the fryer filter- and sediment removal means. A preferably integrated pump will force the filtered oil back to the entrance site of the fryer. In case an additional external filter is applied the preferably pre-filtered oil will be pumped to the external filter positioned nearby the fryer and will from thereon flow back to the entrance side of the fryer. A flow of the frying oil and the products to be fried in the same direction also has the advantage that the highest temperature is at the beginning of the frying, which diminishes the oil uptake of the product during frying.

The fryer preferably comprises a filter and/or sediment-removal within the fryer, preferably within the bath and/or the pump and/or in the tubing to and/or from the pump and/or the microwave chamber, a filter and/or debris removal may be provided.

According to the invention, the frying oil will be exposed to the microwave energy in a microwave chamber, which is according to a preferred embodiment a tube. The microwave chamber, preferably the tube, is preferably made from a material which is at least essentially transparent for microwaves and is hence not or only little heated by the microwave energy. Preferably, the inner area of the pipe is 0.017-0.2 m² and/or the inner diameter of the pipe is preferably between 0.15 and 0.5 m. The microwave chamber and/or the tube to and/or from the microwave chamber may comprise a mixing device. In case of a tube, the mixing device is preferably a static mixer.

According to a preferred embodiment of the present invention, the inventive apparatus may not only comprise one but a multitude of solid-state radio frequency sources. This can be accomplished by using one or more antennas and/or one or more waveguides. Each radio frequency source can be preferably powered individually and each radio frequency source can be preferably controlled, more preferably closed loop controlled, more preferably individually. Preferably, the wavelength, amplitude and/or the direction of the radiation can be controlled.

The solid-state radio frequency sources are preferably provided in an array of n columns and m rows, wherein n is an integer >1 and m is an integer ≥1. Preferably, the solid-state radio frequencies are arranged equidistantly in one row and/or the columns are also arranged equidistantly. In case a multitude of sources, they can be arranged at random.

Preferably, the solid-state radio frequency sources are provided equidistantly around the circumference of the microwave chamber.

Preferably, the inventive processing apparatus comprises means to transport the products to be fried through a bath of hot frying oil, in which the products are preferably submerged. The means are preferably a conveyor, preferably a conveyor-chain. Preferably, two conveyors are provided in parallel, wherein the product is placed between the conveyors to maintain them submerged in the frying oil bath.

Alternatively or additionally, the fryer is designed for batch-processing, wherein the products to be fried are submerged into a hot frying oil bath, for example with a cage.

Preferably, the processing apparatus comprises a control system to control the solid-state radio frequency sources and/or the pump. The control system preferably comprises one or more sensors, whose signal(s) is used to control one or more solid-state radio frequency source(s), preferably individually and/or related to each other and/or the control system controls the pump. In an application pumping the frying oil through a tube, gradually heating of the frying oil and/or very precise temperature control can be achieved by controlling the electromagnetic fields by controlling the power level, frequency and/or phase versus time with such precision that, for example, an even energy distribution in the frying oil chamber or in the frying oil will be achieved. The RF-energy load can be adapted to the progress of the heating process. For instance, during heating the RF-energy load can change. This change in load can be detected, for example via the antenna by measuring the reflected energy. The control system will compare the transmitted energy via the antenna with the reflected energy and will consequently adjust the energy to be transmitted by the antenna. At each solid-state RF energy sources, the amplitude, the frequency and/or the phase can be controlled individually and/or in groups. The antenna may function as a sensor, for example to detect the radiation reflected from the frying oil to be treated.

The sensor can sense one or more properties of the frying oil, for example its temperature and/or the energy absorbed by the frying oil and/or its energy absorption rate, which may change as, for example, the color of the frying oil may change. One sensor can measure what kind of radiation is reflected from the frying oil, for example the wavelength. Since the frying oil is transported during its heating with the RF-radiation, there can be multiple sensors along the transportation path. The local reading of the sensors can be used to control the corresponding local solid-state radio frequency source(s) and/or the solid-state radio frequency source(s) upstream and/or downstream from the respective sensor. In a preferred embodiment, the sensor is a thermocouple, for example a PT100.

In case, the frying oil in the fryer is changed, the sensors can determine one or more properties of the frying oil and adjust and/or control the heating of the frying oil. Afterwards or alternatively, the heating of the frying oil, particularly the setting of the solid-state RF energy source can be adapted to the ageing and/or pollution of the frying oil for example with particles.

Alternatively or additionally, the pump can be controlled, for example based on the signal of the sensor and the capacity of the pump can be increased or decreased to alter the residence time of the frying oil in the microwave chamber, particularly the tube.

The inventive processing apparatus is preferably part of a feed- or food production line, which comprises one or more treatment stations. Upstream from the processing apparatus is preferably a batter.

Another preferred or inventive embodiment of the present invention is therefore a production line, particularly a food production line comprising the inventive apparatus. The line has preferably a common control system, so that a change in the recipe of the products to be produced can be executed for all apparatus in the line centrally. For the fryer, this means for example, that the temperature of the frying oil in the bath and/or the residence time of the product to be fried in the bath can be changed automatically.

According to another preferred embodiment, the inventive apparatus is provided together with a cooling unit and/or a packaging unit.

The problem is also solved with a method to heat a frying oil with radio-frequency waves, wherein the radio-frequency waves are provided with one or more solid-state radio frequency source(s).

The disclosure made regarding this subject matter of the present invention also applies to the other invention and vice versa. Subject matters disclosed regarding this invention can also be combined with subject matters from other inventions of the present application.

Preferably the frying oil is transported from an inlet of a treatment apparatus to an exit of the same apparatus which are spaced apart.

Preferably one or more sensors are provided which measure one or more properties of the frying oil, the product to be fried and/or the radiation reflected from the frying oil and/or the product. The properties are preferably measured at least twice during its treatment with RF-radiation. The changes of the properties are determined and can be taken into account when controlling the solid-state radio frequency source(s) and/or a pump which pumps the frying oil through a microwave chamber, preferably a tube.

Transistor technology generates powerful RF fields. Preferably multiple RF sources will be applied, the sources can be controlled individually and preferably related to each other. For instance, in an application pumping a mass through a tube, gradually heating of the frying oil can be achieved by controlling the electromagnetic fields by controlling the power level, frequency and phase versus time with such precision that an even energy distribution will be achieved. In general, in case of a change in load in a certain spot of the frying oil, the controller can control the specific parameters parameter in that certain spot in order to correct the adverse effects of the load change. For instance, during heating the frying oil load may change. This change in load will be detected via the antenna by measuring the reflected energy. The control system will compare the transmitted energy via the antenna with the reflected energy and will consequently adjust the energy to be transmitted by the antenna.

The inventions are now explained according to the Figures. The explanations apply for all embodiments of the present invention likewise.

FIGS. 1a and 1b show a first embodiment of the present invention.

FIG. 1c shows a second embodiment of the present invention.

A first embodiment of a solid-state RF energized microwave apparatus is depicted in FIG. 1a and 1b , which comprises a multiple solid-state RF sources 2 which each comprises a waveguide 10 and/or an antenna 11. In the present case, the inventive apparatus comprises a multitude, here five, of solid-state RF sources 2, which are provided at the circumference of a frying oil chamber 9 and preferably, equidistantly around the circumference of the of the frying oil chamber. The number of sources 2 in circumferential direction can depend on the efficiency, of the microwaves to heat up frying oil 8 evenly, measured for example by the temperature rise per unit of time. The solid-state RF sources 2 are located in a chamber 7, in the present case defined by housing 3. The housing 3 can be similar to a Faraday cage to prevent electromagnetic waves coming out of the housing. At least inner wall 4 but preferably the entire housing 3 can be made of steel, for instance stainless steel. Inside the chamber 7 and/or inside the housing 3, a frying oil chamber 5, here a microwave tube 5 is provided, which separates the frying oil chamber 5 from the chamber 7, in which the solid-state RF sources 2 are located. The tube material is preferably at least partially, more preferably completely transparent for the microwave energy supplied by the solid-state RF sources 2 and more preferably do not absorb microwave energy and will therefore not be heated up by the microwave energy but, if any, only heated up by the warmed-up product without the build-up of deposit on the inner wall of the tube. Particularly, the tube, particularly its inner wall 6, will not be at a higher temperature than the desired temperature of the frying oil, for example not warmer than 180° C. To effectively convert the microwave energy into increased temperature of the frying oil to be heated, the material of the tube 5 is not metal, but certain plastic materials and/or quartz-materials are suitable, which are more preferably food grade. The frying oil 8 is located within the frying oil chamber 5 and will be heated by one preferably multiple solid-state sources 2 located in chamber 7. This embodiment is, for example, preferred in case cleaning agents used to clean frying oil chamber 5 may not be come in contact with the solid-state sources 2. The tube 5 can also be used to direct the product past the solid-state RF sources 2. If needed, the chamber 7, which surrounds the tube 5 may be cooled to cool the RF-sources.

FIG. 1c shows another embodiment of the present invention. Reference can be made to the description according to FIGS. 1a and b . However, in the present case, there are microwave transparent shielding means 12 which protects the antenna 11 and the waveguide 10 against the frying oil 8. The shielding means are preferably made of a microwave transparent material, for example the material of the tube 5 as described above.

LIST OF REFERENCE SIGNS

-   1 microwave apparatus -   2 solid-state RF energy source -   3 housing -   4 inner wall housing 3 -   5 frying oil chamber, microwave tube -   6 inner wall microwave tube 5 -   7 solid-state source chamber -   8 frying oil -   9 frying oil chamber -   10 waveguide -   11 antenna -   12 microwave transparent shielding means 

1. Processing apparatus, in which a product is transported from a product-entry to a product-exit and is fried in a frying oil bath, wherein the frying oil is pumped by a pump through a microwave chamber and is thereby heated, wherein the microwave chamber is provided as a tube, the microwave chamber comprises at least one solid-state radio frequency sources, wherein the frying oil is configured to flow out of the frying oil bath towards the microwave chamber where it is heated and then the frying oil is configured to flow back into the microwave chamber, wherein a flow direction of the of the frying oil is the same as a direction of a flow of the product, and wherein the processing apparatus comprises a filter in the tube of the microwave chamber.
 2. Processing apparatus according to claim 1, wherein the microwave chamber is at least transparent for microwaves.
 3. Processing apparatus according to claim 1, wherein the solid-state radio frequency sources are provided in an array of n columns and m rows, wherein n is an integer >1 and m is an integer ≥1.
 4. Processing apparatus according to claim 1, wherein the solid-state radio frequency sources are provided equidistantly around a circumference of a microwave chamber.
 5. Processing apparatus according to claim 1, wherein the processing apparatus comprises an inlet and an outlet, which are spaced apparat from each other.
 6. Processing apparatus according to claim 1, wherein the pump transports the frying oil past the solid-state radio frequency sources.
 7. Processing apparatus according to claim 1, wherein the processing apparatus comprises a control system that is configured to control the solid-state radio frequency sources and/or the pump.
 8. Processing apparatus according to claim 1, wherein the processing apparatus comprises a sensor that is configured to measure at least one property of the frying oil and/or one property of radiation reflected from the frying oil, wherein a signal of the sensor is utilized by the control system.
 9. (canceled)
 10. Method to heat a frying oil with radio-frequency waves, wherein the radio-frequency waves are provided with one or more solid-state radio frequency wherein a setting of the solid-state RF energy sources is adapted to an ageing and/or a pollution of the frying oil with particles.
 11. Method according to claim 10, wherein the frying oil is transported from an inlet to an exit of a processing apparatus which are spaced apart.
 12. Method according to claim 11, wherein the frying oil is transported continuously and or intermittently.
 13. Method according to claim 10, wherein one or more sensors are provided which measure one or more properties of the frying oil and/or radiation reflected from the frying oil.
 14. Method according to claim 13, wherein signal of the one or more sensors is utilized to control the solid-state radio frequency source and/or a pump which transports the frying oil past the solid-state radio frequency sources.
 15. Method according to claim 10, wherein the frying oil is heated, disinfected and/or pasteurized, sterilized. 